1. Field of the Invention
The present invention relates to a device for printing a droplet on a substrate or ink on a sheet of paper, and more particularly, to a device for printing a droplet including bioparticles such as nucleic acids (e.g., probe DNA, RNA, PNA and LNA), proteins (e.g., antigen and antibody), oligopeptides, eukaryotic cells (e.g., human cells, animal cells and vegetable cells), viruses and bacteria on a substrate using an electric charge concentration effect and fixing the droplet to the substrate to manufacture a biochip, and a device for printing ink on a sheet of paper using an electric charge concentration effect by dropping ink onto the sheet of paper to print contents of computer document files or photographic files.
2. Description of the Related Art
As a result of the epoch-making development of the Human Genome Project, there is an increasing need for methods of rapidly providing a large amount of genetic information for the diagnosis, treatment and prevention of genetic disorders. Although the Sanger method for analyzing nucleotide sequences has been constantly developed through the development and automation of a polymerase chain reaction (“PCR”) method, in which DNAs are duplicated, complex and extensive time, labor, expense and expertise are required to perform the Sanger method. Thus, a large number of genes cannot be analyzed using the Sanger method. As a result, new systems for analyzing nucleotide sequences are continuously being researched. In the last several years, there have been advances in many fields relating to the manufacture and application of biochips.
A biochip, that is, a biological microchip, includes a solid substrate which is made of, for example, silicon, surface-modified glass, polypropylene, or activated polyacrylamide and combined with biomolecules such as nucleic acids, proteins and cells. Biochips can be used to analyze gene developing patterns, genetic defects, protein distribution, or various kinds of reaction patterns.
If a target material to be analyzed is applied to the biochip, the target material hybridizes with probes immobilized on the biochip. The hybridization is optically or radiochemically detected and analyzed to identify the target material. For example, if a fragment of target DNA to be analyzed is applied to the DNA chip (or DNA microarray) having probes, the target DNA complementarily hybridizes with the probes immobilized on the biochip. The hybridization is detected and analyzed using various detecting methods to identify the nucleotide sequence of the target DNA, which is called sequencing by hybridization (“SBH”).
A printing device used to manufacture a biochip or DNA microarray includes a droplet generating member disposed above a substrate in order to drop droplets on the substrate. The volume of the droplet is reduced as time elapses when the droplet protruding downward from the droplet generating member. The droplet evaporates in proportion to the surface area of the droplet,. When the volume of the droplet is reduced, a spot size of the droplet to be printed on the substrate is reduced. However, the conventional printing device does not include a member for maintaining the size of the droplet in order to ensure a constant spot size. Thus, a desired spot size cannot be obtained using the conventional printing device.
When a biochip or DNA microarray is manufactured, a fine droplet is dropped onto the substrate to form the spot, and thus, small variations in the size of the volume of the droplet have a large effect on the size of the spot formed on the substrate. Therefore, the size of the volume of the droplet formed on the lower portion of the droplet generating member should be maintained constant in order to manufacture a microarray including spots of uniform size. If the size of the volume of the droplet formed on the lower portion of the droplet generating member is not maintained to be constant, the size of the spots formed on the substrate cannot be maintained uniformly. Thus, excellent performance of the DNA microarray, that is, the precise analysis of a DNA sequence, cannot be obtained.